1. Field of the Invention
The present invention relates to a vehicular door mirror device.
2. Description of the Related Art
There are vehicles such as automobiles disposed with, for example, tire pressure monitoring systems (TPMS) that monitor the air pressure of the tires, remote keyless entry (RKE) systems for remotely unlocking and locking the doors, and/or television (TV) receivers. These types of tire pressure monitoring systems, remote keyless entry systems and TV receivers are actuated when they receive radio transmissions from the outside of the vehicle cabin.
Here, as receiving devices for receiving such radio transmissions, there are receiving devices that include an antenna attached to the inside of a door mirror device (the inside of a door mirror enclosure) (e.g., see Japanese Patent Application Publications Nos. 2004-130875 and 2004-168153). A dedicated base plate disposed inside the door mirror enclosure, for example, is electrically connected to the antenna and serves as the ground of the antenna.
However, when trying to obtain a sufficient ground with a dedicated base plate (when trying to sufficiently ground the antenna to a dedicated base plate), it is necessary to enlarge the area (size) of the dedicated base plate. For this reason, there has been the problem that the dedicated base plate must be large and is difficult to make compact.
There are also configurations which obtain the ground from the vehicle body, without obtaining the ground from a dedicated base plate, by connecting an electrical cable (e.g., an AV cable) to the antenna and disposing the electrical cable inside the vehicle body.
However, because the electrical cable must be disposed inside the vehicle body, the work of disposing the electrical cable is complicated. Also, after this work of disposing the electrical cable, the disposed position of the electrical cable ends up being changed merely when the door mirror switches between its accommodated state and its erect state because the electrical cable is disposed inside the vehicle body. For this reason, there has been the problem that the antenna characteristics end up fluctuating.